The overall objective of this proposal is to examine the immunobiological relationship between host and parasite in experimental African trypanosomiasis. The role of trypanosome antigen-specific B and T cell responses, and the role of the macrophage, in providing protection and controlling parasitemia are being assessed. The role of the parasite-specific immune response in inducing pathology is also being determined. Finally, the ability of the trypanosome to modulate host immune responses to the trypanosome surface antigens is being measured, and efforts are being made to manipulate such parasite-specific responses so as to provide more protection and less pathology. Thus, the proposed research will carefully dissect numerous aspects of the immunology in the host-parasite relationship in experimental African trypanosomiasis, and addresses questions of fundamental importance in medical and veterinary tropical disease.